1. Field of the Invention
The present invention relates to a production method of a hydroxyl-containing polymer, more particularly to a production method of a hydroxyl-containing polymer preferably usable for carriers of diagnosis drugs and pharmaceutical products, chromatography carriers, viscosity adjustment agents, resin molding materials, coating material additives, crosslinking/curing agents, and cosmetic product additives.
2. Description of the Related Art
So far, in the case of producing polymers by polymerizing monomer mixtures containing hydroxyl-containing monomers such as hydroxyethyl(meth)acrylate, polyethylene glycol(meth)acrylate, since the monomers are water-soluble, a method of solution polymerization carried out in an aqueous solution, a method of emulsion polymerization carried out in water, a method of suspension polymerization carried out in water, and a method of reversed-phase suspension polymerization have been known as methods of producing such polymers.
For example, production methods of solution polymerization of monomer mixtures containing a carboxyl-containing monomer and a monomer having polyethyleneglycol chain in a mixed solvent of a water-soluble organic solvent and water have been disclosed (e.g., refer to Japanese Patent Application Laid-Open (JP-A) No. 3-239709). However, in the case of adding a hydrophobic monomer such as styrene, phase-separation takes place to make it difficult to obtain copolymers.
Further, techniques of obtaining polymers by emulsion polymerization of a monomer mixture containing a carboxyl-containing monomer and a monomer having polyethyleneglycol chain in water have been disclosed (e.g. refer to JP-A Nos. 60-122770, 1-111769, and 7-10943). However, since the particles to be obtained by the emulsion polymerization have a size equal to 1 μm or smaller, washing of the particles for removing impurities such as the residual monomers, surfactants and the like is difficult and thus the particles are unsuitable for uses as carriers of diagnosis drugs and pharmaceutical products carriers, chromatography carriers, which are susceptible to the impurities.
Further, methods of obtaining polymers by suspension polymerization of hydroxyethyl (meth) acrylate with a monomer mixture containing a hydrophobic monomer and solvent such as diethylene glycol dimethacrylate, glycidyl methacrylate, and toluene in water have been disclosed (e.g., refer to JP-A No. 2001-318086). However, since hydroxyethyl (meth) acrylate is water-soluble, when the suspension polymerization is carried out in water, polymerization takes place even in water to result in occurrence of disadvantageous agglomeration of particles during polymerization. Also, since the water-soluble monomer is distributed in oil droplets and water, it is difficult to produce polymers with desired copolymerization ratios and further since the methods require solvents, the solvents have to be removed after the polymerization and therefore it is required to remove the solvents from polymers.
On the other hand, as one method of polymerization of water-soluble ethylenic unsaturated monomers, so-called reversed-phase suspension polymerization methods for carrying out polymerization by suspending and dispersing an aqueous monomer solution in a hydrophobic solvent have been known well and for example, methods of using nonionic surfactants of HLB 3 to 6 (e.g. refer to JP-A No. 61-157513) and methods of using copolymers of α-olefins and α,β-unsaturated polycarboxylic acid anhydrides, or their derivatives (e.g. refer to JP-A No. 62-95308) have been known. However, the reversed-phase suspension polymerization methods can be applicable mainly for water-soluble monomers and the methods are difficult to be applied for copolymerization of hydrophobic monomers.
On the contrary, methods of copolymerization with hydrophobic monomers have also been disclosed (e.g. refer to JP-A No. 2003-147005). However the content of copolymerizable hydrophobic vinyl monomers is limited to 5% by mass in relation to the water-soluble vinyl monomers, and in such a manner it has been difficult for the reversed-phase suspension polymerization methods to carry out copolymerization using a large quantity of hydrophobic monomers.